In August 1519 Hernán Cortés was marching toward the Aztec capital Tenotchtitlán, when he saw something "not a little marvelous":

Eight leagues from this city of Cholula there are two marvelously high mountains [Popocatépetl and Ixaccihuatal] whose summits still at the end of August are covered with snow so that nothing else can be seen of them. From the higher of the two both by day and night a great volume of smoke often comes forth and rises up into the clouds as straight as a staff, with such force that although a very violent wind continuously blows over the mountain range yet it cannot change the direction of the column. Since I have ever been desirous of sending your Majesty a very particular account of everything that I met with in this land, I was eager to know the secret of this which seemed to me not a little marvelous, and accordingly sent ten men such as were well fitted for the expedition with certain natives to guide them to find out the secret of the smoke, where and how it arose. These men set out and made every effort to climb to the summit but without success on account of the thickness of the snow, the repeated wind storms in which ashes from the volcano were blown in their faces and also the great severity of the temperature, but they reached very near the top, so near in fact that being there when the smoke began to rush out, they reported that it did so with such noise and violence that the whole mountain seemed like to fall down....

Misenum
For several days past there had been earth tremors which were not particularly alarming because they are frequent in Campanoa: but that night the shocks were so violent that everything felt as if it were not only shaken but overturned.

Misenum
On 24 August, in the early afternoon, my mother drew his attention to a cloud of unusual size and appearance.

It was not clear at that distance from which mountain the cloud was rising (it was afterward known to be Vesuvius); its general appearance can best be expressed as being like an umbrella pine, for it rose to a great height on a sort of trunk and then split off into branches.

Stabiae
[Pliny's uncle sails across the bay to help evacuate people]
Ashes were already falling, hotter and thicker as the ships drew near, followed by bits of pumice and blackened stones, charred and cracked by the flames: then suddenly they were in shallow water, and the shore was blocked by debris from the mountain.

Stabiae
[the eruption intensifies; Pliny the Elder stays at Stabiae and is overcome by fumes the following morning]
Meanwhile on Mount Vesuvius broad sheets of fire and leaping flames blazed at several points, their bright glare emphasized by the darkness of night.

By this time the courtyard giving access to his room was full of ashes mixed with pumice stones, so that its level had risen, and if he had stayed in the room any longer he would never have got out.

They debated whether to stay indoors or take their chance in the open, for the buildings were now shaking with violent shocks, and seemed to be swaying to and fro as if they were torn from their foundations. Outside, on the other hand, there was the danger of falling pumice stones, even those these were light and porous; however, after comparing the risks they chose the latter.

Elsewhere there was daylight by this time, but they were still in darkness, blacker and denser than any ordinary night....

Then the flames and smell of sulphur which gave warning of the approaching fire drove the others to take flight and roused him to stand up. He stood leaning on two slaves and then suddenly collapsed, I imagine because the dense fumes choked his breathing....

Misenum
[Pliny the Younger and his aunt flee Misenum in the morning]
By now it was dawn, but the light was still dim and faint. The buildings round us were already tottering, and the open space we were in was too small for us not to be in real and imminent danger if the house collapsed. This finally decided us to leave the town. We were followed by a panic-stricken mob of people....

We also saw the sea sucked away and apparently forced back by the earthquake: at any rate it receded from the shore so that quantities of sea creatures were left stranded on dry sand. On the landward side a fearful black cloud was rent by forked and quivering bursts of flame, and parted to reveal great tongues of fire, like flashes of lightning magnified in size.

Soon afterward the cloud sank down to earth and covered the sea; it had already blotted out Capri and hidden the promontory of Misenum from sight.

Ashes were already falling, not as yet very thickly. I looked round: a dense black cloud was coming up behind us, spreading over the earth like a flood.

We had scarcely set down to rest when darkness fell, not the dark of a moonless or cloudy night, but as if the lamp had been put out in a closed room. You could hear the shrieks of women, the wailing of infants, and the shouting of men....

A gleam of light returned, but we took this to be a warning of the approaching flames rather than daylight. However, the flames remained some distance off; then the darkness came on once more and ashes began to fall again, this time in heavy showers. We rose from time to time and shook them off, otherwise we should have been buried and crushed beneath their weight.

Misenum
[the eruption subsides]
At last darkness thinned and dispersed into smoke or cloud; then there was genuine daylight, and the sun actually shone out, but yellowish as it is in an eclipse. We were terrified to see everything changed, buried deep in ashes like snowdrifts. We returned to Misenum.... Fear predominated, for the earthquakes went on....